Kidney is an important organ that maintains body homeostasis. It controls body fluid volume, blood ion concentration and pH; secretes waste products such as metabolic wastes, toxin and drug inter alia; and performs blood pressure control, metabolic and endocrine function. Also, it helps calcium absorption in small intestine by activating vitamin D, and it is involved in various hormone synthesis.
Renal disease means a status where overall function of kidney is lowered or abnormalities are incurred due to failure of kidney to perform secretory, control, metabolic and endocrine function normally. Hypofunction caused by kidney injury incurs enlarged kidney and related structures, kidney atrophy, body fluid volume change, electrolyte imbalance, metabolic acidosis, gas exchange disorder, anti-infective function impairment and uremic toxin accumulation inter alia.
Renal diseases are categorized into acute renal failure and chronic renal failure depending on its progression; or into glomerulonephritis due to deposition of vascular complex, diabetic nephropathy accompanied with diabetes or hypertensive renal disease accompanied with hypertension, toxic nephropathy due to drug administration such as antibiotics or anticancer drugs and bacterial infection inter alia depending on cause of the disease.
Irrespective of types of causative renal diseases, when glomerular filtration rate drops below 50% due to chronic progression of renal disorder, in most cases the glomerular filtration rate decreases continuously, end-stage renal failure occurs eventually and may lead to death in severe cases due to complications such as hematological abnormalities, neurological complications, gastrointestinal complications, infection or osteodystrophy inter alia.
Renal diseases are increasing every year worldwide and often discovered when the disease is developed to end-stage renal failure because there are no symptoms or symptoms that are hard to recognize. According to the analysis on the beneficiaries of Medicare that was reported to USRDS (United States Renal Data System), 2.7% of prevalence rate of end-stage renal failure in year 2000 was increased to 8.5% in 2009. In case of South Korea, it was reported that end-stage renal failure patients were 37.1% in total in 2010, which was increased by an annual average of 8.2% compared to that of 2006. These phenomena are closely related to the increase of diabetic nephropathy due to increase of obesity and diabetes patients.
DPP-IV (Dipeptidyl peptidase-IV) is a protein that is also known as adenosine deaminase complexing protein 2 or CD26, and it is encoded by DPP-IV genes. DPP-IV is reported to be involved in immune response, and known as performing an important role in glycometabolism by involving in degradation of GLP-1 (Glucagon-like peptide-1) that promotes insulin secretion and inhibits glucagon secretion. DPP-IV is reported to be dispersed a lot in renal proximal tubule cells, glomerular basement membrane and podocytes. DPP-IV inhibitor has functions of decreasing blood glucose level by inhibiting the degradation of GLP-1 to maintain its activity, and DPP-IV inhibitor is currently being used as an antidiabetic agent because it has no side effects that induce hypoglycemia.